MIP-1β production and degranulation of CD56negCD16posNK cell subset after K562 cell stimulation. PBMCs from healthy children (Nandi and Kisumu; n = 7) and eBL children (n = 7) were stimulated with K562 cells in a functional in vitro killing assay. NK cell subsets were defined by CD56 and CD16 expression levels. (A) Percentage of MIP-1βpos NK cells in each subset, with and without stimulation. (B) Percentage of TNF-αpos NK cells in each subset, with and without stimulation. (C) Comparison of MIP-1β, TNF-α, CD107a, and IFN-γ positive cells after K562 cell stimulation between the CD56dimCD16pos and CD56negCD16pos NK cell subsets. The Wilcoxon test was used for related data, and Mann-Whitney U test was used for nonrelated data. Data are mean ± SD. *P < .05.